OMAD Crash at the 18 Hour Mark?

I’ve been doing OMAD ~4-5 times a week for the last month or so. Pretty consistently around the 18 or 19 hour mark into the intermittent fast I’ll feel a crash. Like brain fog, zombie like feeling, mild headaches, eyes heavy, and my mouth wants to be droopy.

Any thoughts to this? Is this when I’d drink some salt water for electrolytes or are there other issues that could be going on too? Just wondering how I can prevent this.